1. Field of the Invention
The present invention relates generally to a pressure controllable incubation system. More particularly, the present invention relates to a pressure controllable incubation system capable of constantly maintaining a concentration of carbon dioxide while keeping a pressure chamber, in which living organisms to be cultured are placed, at a pressure higher than atmospheric pressure.
2. Description of the Prior Art
Such an incubation system is applied to a research on the diseases of the circulatory system relating to endothelial and muscular cells of blood vessels, glomerular cells, etc. of various animals cultured under pressure (about 1.2 ata) corresponding to high blood pressure of a human being, a research on the dentistry relating to alveolar bone and periodontal ligament cells, a research on the influence which mechanical and physical stimuli such as pressure exert on chondrogenic differentiation of cartilaginous cells and stem cells, and so on. Furthermore, the incubation system is also applied to a research on hyperbaric oxygen therapy that has been used to cure injuries, hypoxia, decompression sickness, diver's disease, carbon monoxide poisoning, etc. for a long time by pressurizing 100% oxygen outside the organism at 2 through 4 ata for a short time, and a research on oxidative stress and antioxidants of cells or individuals.
In order to study biological influences which the “pressure” exerts on the cells or organisms such as nematodes indispensable to make this research, various conditions such as pressure, temperature, concentration of carbon dioxide, etc. must be invariably maintained. To this end, an apparatus or system for applying the pressure to the cells or organisms such as nematodes has been provided.
This related apparatus or system includes a technique of injecting 95% air and 5% carbon dioxide into a big bottle using a 25-gauge needle (Watanabe et al., Saga University in Japan, 1987), a technique of directly inserting a pressure chamber into a carbon dioxide incubator and adjusting a concentration of carbon dioxide to 5% (Kato et al., Kurume University in Japan, 1994), and so on. Further, a technique of installing a variety of lead ingots on a piston and adjusting pressure (Yamamoto et al., Osaka University in Japan, 1991) was proposed. Recently, a technique of measuring and adjusting pressure in an incubator using a solid-state sensor and a compressor at the same time (Chris Healey et al., The University of Vermont in USA, 2003) has been proposed.
Most of these related incubation systems employ the technique of applying pressure to a chamber using an air or oil pump system and a solenoid valve, and are not suitable to meet experimental conditions for culturing the cells or organisms such as nematodes, i.e. conditions for maintaining the carbon dioxide concentration of 5% for a long time. For this reason, the related pressure controllable incubation systems for culturing living organisms have difficulty in obtaining reliable accurate results.
Further, these incubation systems are structurally complicated to increase a volume of constituents installed therein, and require careful management due to troublesome operation and frequent malfunction. Furthermore, these incubation systems are not suitable for an experiment of applying the pressure to the nematodes, which are small experimental animals having a very high value of the biological research. Thus, the influences which the pressure exerts on the organisms are merely observed within the limits of the animal cells. Consequently, the researches on the influences which the pressure exerts on the individuals make difficult progress.